[Amps] Suppressors

[Peter Chadwick]

Steve said:
>What we want from the suppressor is low resistance between the anode and 
blocking cap/tune C at hf, and high resistance at vhf. Given that 
there's a series circuit from the anode through the suppressor, blocking 
cap and tune C to ground, looking at the series resistance the 
suppressor introduces is the useful way to view it<

This is where I disagree. A higher impedance at VHF between the anode and the blocking capacitor means that there is more gain at VHF - at least, at the anode connector. A lower Q means less phase shift (and also lower impedance), so the phase margin improves. Thus the inductor shunted by a resistor, having an impedance that tends towards the resistor impedance as the frequency increases, gives an upper limit to the VHF gain. This improves matters on a Bode plot.
(I've always had trouble with Nyquist diagrams and normalisation and what it really means, and exactly what parameters they are at 1 and -1 or wherever it is they always oscillate, etc...)
73
Peter G3RZP